In recent years, using LTE technology to implement MTC (Machine Type Communication) device connection and communication has attracted industry attention. In many scenarios, these low energy consumption devices are wearable devices and are less distant from the smartphone around people. At this time, using the smartphone as a relay device of the wearable device, that is, using the UE-to-Network communication mode can reduce the energy consumption of the wearable device.
Two relay scenarios are mainly studied in Release 14, as shown in FIGS. 1 and 2, where Uu represents a communication link between an evolved Node B (eNB) and relay user equipment (UE), PC5 represents a communication link between the relay UE and a remote UE, UL represents an uplink, and DL represents a downlink. FIG. 1 illustrates a two-way relay scenario in which the remote UE transmits uplink and downlink data through the relay UE, that is, the remote UE does not directly communicate with the eNB, and both uplink and downlink transmissions are completed by the relay UE. FIG. 2 illustrates a one-way relay scenario in which the remote UE only transmits uplink data through the relay UE, and downlink data is still directly received from the eNB through the Uu link.